Commit Graph

2 Commits

Author SHA1 Message Date
Roman Lebedev 772ede3d5d
[InstCombine] Sink sub into hands of select if one hand becomes zero. Part 2 (PR44426)
This decreases use count of %Op0, makes one hand of select to be 0,
and possibly exposes further folding potential.

Name: sub %Op0, (select %Cond, %Op0, %FalseVal) -> select %Cond, 0, (sub %Op0, %FalseVal)
  %Op0 = %TrueVal
  %o = select i1 %Cond, i8 %Op0, i8 %FalseVal
  %r = sub i8 %Op0, %o
=>
  %n = sub i8 %Op0, %FalseVal
  %r = select i1 %Cond, i8 0, i8 %n

Name: sub %Op0, (select %Cond, %TrueVal, %Op0) -> select %Cond, (sub %Op0, %TrueVal), 0
  %Op0 = %FalseVal
  %o = select i1 %Cond, i8 %TrueVal, i8 %Op0
  %r = sub i8 %Op0, %o
=>
  %n = sub i8 %Op0, %TrueVal
  %r = select i1 %Cond, i8 %n, i8 0

https://rise4fun.com/Alive/aHRt

https://bugs.llvm.org/show_bug.cgi?id=44426
2020-01-04 17:30:51 +03:00
Roman Lebedev d2b79c76be
[NFC][InstCombine] 'subtract from one hands of select' pattern tests (PR44426)
https://bugs.llvm.org/show_bug.cgi?id=44426
2020-01-04 17:30:51 +03:00